1. Technical Field
This invention is used to measure the hardness of muscle or muscle compartment through means of a portable and mechanically simple device that measures the force necessary to compress the muscle by a given amount. This is of relevance to the field of medicine dealing with musculoskeletal problems in which muscle hardness is directly related to muscle tone or abnormal process occurring within or around the muscle.
2. Description of the Prior Art
Muscles of the limb lie within compartments which are bound by fasciae. In the physical examination, the palpation of the muscle by the physician provides an important subjective data which lends crucial insight into the normal and abnormal processes occurring within the muscle or the muscle compartment. There are numerous neuromuscular conditions which manifest as palpable changes in muscle tone varying from flaccid hypotonia to spastic hypertonia. Moreover, there is a dangerous clinical entity known as compartment syndrome which manifests as increase in muscle hardness which if untreated can result in permanent disability and deformity. Although the tone of the muscle itself does not change with this syndrome, the increased pressure build-up in the interstitial tissue of the muscle compartment manifests as hardness which can be palpated in similar manner.
In current medical practice, there exists no device or means to measure the hardness of a patient's muscle or muscle compartment that is quick and easy to use in routine clinical setting. There are patents which assess human tissue hardness by means of apparatus having electronic components to measure force applied and/or distance displaced (Roush et al U.S. Pat. No. 5,038,795; Leveque U.S. Pat. No. 4,159,640; Leonard et al U.S. Pat. No. 6,063,044; Steinberg 6,659,967). However, the complexity associated with use, design, cost, and the increased number of components that can fail contributed to the reluctance of medical community in implementing the routine use of such devices for routine clinical purpose.
As mentioned above, diagnosing compartment syndrome is one application of a device which measures hardness of muscle. As shown in orthopedic literature by Steinberg (Steinberg 1994), increased intra-compartmental pressure manifests itself clinically by hardness of the muscle compartment which can then be measured non-invasively. But for the reasons iterated above, such device (Steinberg U.S. Pat. No. 6,659,967) is not part of routine clinical practice.
A device that is in current clinical practice for diagnosis of compartment syndrome is a needle and syringe pressure transducer system under the U.S. Pat. No. 4,817,629. This invasive device requires the needle to penetrate into the individual muscle compartments in question and is a direct measurement of each compartment pressure. Although it gives the only quantitative data in making the diagnosis (pain, hardness, decreased sensation, and decreased pulse comprise the subjective data), the obvious disadvantages of this method are numerous. For instance, the patients presenting with compartment syndrome of the leg or a suspected compartment syndrome already have exquisitely painful limbs which are further subject to the pain induced by introduction of the needle deeply into their muscle compartments at least four times (there are 4 compartments in the leg). Moreover, in cases of equivocal clinical findings, it is commonplace to perform repeat compartment measurements in order to monitor whether the symptoms will progress into frank compartments syndrome, and this leads to significant increase in pain and distress to the patient. There are also risks of injuring the arteries or nerves with this invasive technique which is not routinely performed under any imaging guidance. Also, microorganisms can be introduced into the deep compartments if meticulous aseptic techniques are not employed and result in infection. In addition, the physician is at risk of injuring him/herself with the needle especially if the patient does not hold still. Thus, a functional alternative to this invasive method is warranted.